[Python-checkins] bpo-45614: Fix traceback display for exceptions with invalid module name (GH-29726) (GH-29826)

[iritkatriel]

https://github.com/python/cpython/commit/4d2cc3ed46d2453bad92243128e237e7febca714
commit: 4d2cc3ed46d2453bad92243128e237e7febca714
branch: 3.10
author: Irit Katriel <1055913+iritkatriel at users.noreply.github.com>
committer: iritkatriel <1055913+iritkatriel at users.noreply.github.com>
date: 2021-11-29T10:07:24Z
summary:

bpo-45614: Fix traceback display for exceptions with invalid module name (GH-29726) (GH-29826)

(cherry picked from commit 4dfae6f38e1720ddafcdd68043e476ecb41cb4d5)

files:
A Misc/NEWS.d/next/Core and Builtins/2021-11-23-12-06-41.bpo-45614.fIekgI.rst
M Lib/test/test_traceback.py
M Lib/traceback.py
M Python/pythonrun.c

diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index ba03ce46294c5..18cd4aba24af2 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -785,6 +785,17 @@ def test_message_none(self):
         err = self.get_report(Exception(''))
         self.assertIn('Exception\n', err)
 
+    def test_exception_modulename_not_unicode(self):
+        class X(Exception):
+            def __str__(self):
+                return "I am X"
+
+        X.__module__ = 42
+
+        err = self.get_report(X())
+        exp = f'<unknown>.{X.__qualname__}: I am X\n'
+        self.assertEqual(exp, err)
+
     def test_syntax_error_various_offsets(self):
         for offset in range(-5, 10):
             for add in [0, 2]:
diff --git a/Lib/traceback.py b/Lib/traceback.py
index 901b99476aaf8..d6a010f415758 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -604,6 +604,8 @@ def format_exception_only(self):
         stype = self.exc_type.__qualname__
         smod = self.exc_type.__module__
         if smod not in ("__main__", "builtins"):
+            if not isinstance(smod, str):
+                smod = "<unknown>"
             stype = smod + '.' + stype
 
         if not issubclass(self.exc_type, SyntaxError):
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-11-23-12-06-41.bpo-45614.fIekgI.rst b/Misc/NEWS.d/next/Core and Builtins/2021-11-23-12-06-41.bpo-45614.fIekgI.rst
new file mode 100644
index 0000000000000..4255e1885ad67
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-11-23-12-06-41.bpo-45614.fIekgI.rst	
@@ -0,0 +1 @@
+Fix :mod:`traceback` display for exceptions with invalid module name.
\ No newline at end of file
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 5704bcc7589f3..0f1794acec73a 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -972,7 +972,7 @@ print_exception(PyObject *f, PyObject *value)
         {
             Py_XDECREF(modulename);
             PyErr_Clear();
-            err = PyFile_WriteString("<unknown>", f);
+            err = PyFile_WriteString("<unknown>.", f);
         }
         else {
             if (!_PyUnicode_EqualToASCIIId(modulename, &PyId_builtins))